# Aero Commander 500 family

The Aero Commander 500 family is a series of light twin piston-engined and turboprop aircraft originally built by the Aero Design and Engineering Company in the late 1940s, renamed the Aero Commander company in 1950, and later a division of Rockwell International in 1965. Final production occurred in 1986 under the Gulfstream Aerospace name. The initial production version was the 200 mph (320 km/h; 170 kn), seven-seat Aero Commander 520. An improved version, the 500S, manufactured after 1967, is known as the Shrike Commander. Larger variants are known by numerous model names and designations, ranging up to the 330 mph (530 km/h; 290 kn), 11-seat Model 695B/Jetprop 1000B turboprop. As of recent, the Aero Commander is known as the Twin Commander.

## Design and development

The idea for the Commander light business twin was conceived by Ted Smith, a project engineer at the Douglas Aircraft Company. Working part-time after hours throughout 1944, a group of A-20 engineers formed the Aero Design and Engineering Company to design and build the proposed aircraft with a layout similar to their A-20 bomber. Originally, the new company was going to build three pre-production aircraft, but as the first aircraft was being built, they decided to build just one prototype. The final configuration was completed in July 1946 and was designated the Model L3805.
Registered NX1946, the prototype first flew on 23 April 1948. The L3805 accommodated up to five people and was powered by two Lycoming O-435-A piston engines., it was an all-metal high-wing monoplane with retractable undercarriage using components from a Vultee BT-13 Valiant. The market segment planned for this aircraft to be sold to small feeder airliner firms and was originally designed to carry seven passengers, but instead found use in the private business aircraft and military market. Walter Beech test flew the aircraft in 1949 and expressed interest in buying the project, but passed on it, to instead develop the Beechcraft Twin Bonanza. Fairchild Aircraft also evaluated the prototype at its Hagerstown, Maryland, headquarters.
The prototype flew successfully and the company leased, at no cost, a new 26,000 square feet (2,400 m$^2$) factory at Bethany near Oklahoma City to build a production version, certified on 30 June 1950. Nearly 10,000 hours of redesign work went into the model, including more powerful Lycoming GO-435-C2 engines, with a combined rating of 520 horsepower (390 kW). The production model was named the Commander 520. The first Commander 520 was rolled out of the new factory in August 1951. Serial number 1 was used as a demonstrator, then sold in October 1952 to the Asahi Shimbun Press Company of Tokyo.

## Operational history

In military service it was initially designated the L-26, though in 1962 this was changed to U-4 for the United States Air Force and U-9 for the United States Army.
Under ownership of Rockwell in the 1960s, World War II pilot R. A. "Bob" Hoover demonstrated the Shrike Commander 500S for decades in a variety of "managed energy" routines, including single-engine and engine-out aerobatics. His Shrike Commander is displayed in the colors of his last sponsor, Evergreen International Aviation, at the Steven F. Udvar-Hazy Center of the Smithsonian National Air and Space Museum. Bob Odegaard continued the tradition in 2012, flying a 1975 Shrike 500S in a Bob Hoover tribute routine.
One U-4B became a presidential transport aircraft for Dwight D. Eisenhower between 1956 and 1960. This was the smallest "Air Force One", and the first to wear the now-familiar blue-and-white livery. This aircraft is now owned by the Commemorative Air Force.
As of 2004 Shrike Commanders remained in service with the United States Customs Service, United States Coast Guard, and United States Forest Service.
A single 560F was operated by the Belgian Air Force as the personal transport of the late king Baudouin of Belgium from 1961 to 1973.
According to the July 1, 1968, Frontier Airlines system timetable, series 500 aircraft were being operated on scheduled passenger flights by Combs Aviation on behalf of Frontier via a contract agreement with service to several smaller communities in Montana and Wyoming at this time.
The unpressurized, long-fuselage 680FL was operated as a small package freighter by Combs Freightair in the 1970s and 1980s, and by Suburban Air Freight in the 1980s and 1990s. The aircraft was popular with pilots, because it was extremely "pilot friendly" and with its 380 hp (280 kW) supercharged engines did well in icing meteorological conditions. A number are still operated on contracts for cargo and fire control applications, as their piston engines offer good fuel specifics at low altitudes and longer loiter times. Suburban retired their last 680FLs in the first half of 2024.

### Wing spar fatigue

Beginning in June 1991, senior engineers met with FAA officials to discuss concerns over the Aero Commander's main wing spar, which was believed to be susceptible to stress fatigue and subsequent cracking, and was believed to have resulted in a number of fatal crashes. From approximately 1961 to 1993, 24 aircraft crashed when spar failures caused the loss of the wing in flight. 35 more spars were found cracked during inspections.

### Single-engine safety

In 1950, when the developers were working to satisfy Civil Aeronautics Authority (CAA) regulations for certification of the 500, they chose a novel method of demonstrating its single-engine safety and performance: they removed one of the two-bladed propellers, secured it in the aft cabin, and flew from Bethany to Washington, D.C., on one engine. There they met with CAA personnel, then replaced the propeller and returned to Oklahoma in the conventional manner. The flight received nationwide coverage in the press.
In 1979, the National Transportation Safety Board reviewed light-twin engine-failure accidents, involving the 24 most popular model-groups of light twins between 1972 and 1976. They found that the piston-engined twin-Commanders had averaged slightly over 3.4 engine-failure accidents per hundred-thousand hours, the second worst number of all aircraft under review. The most engine failures were suffered by the small-engine versions of the Piper Apache, at 6.9 failures per hundred thousand hours; the third-worst, the Beechcraft Travel Air, averaged 2.9 failures; the average for all models was only 1.6.
Countering the statistical evidence, Rockwell demonstration pilot Bob Hoover's famous airshow stunt routine, with the Shrike Commander, included a full aerobatic routine performed first with both engines, then with one engine out (and the critical engine, at that), then both engines out, and gliding. Then in his final airshow performance, in a supreme demonstration of conservation of momentum, he did all that, then landed the Shrike Commander dead stick (engines off), coasted the airplane down the runway then from the runway down the taxiway and silently let the craft roll slowly to a full stop right in front of the crowd.
The turboprop twin-Commanders—with much more powerful engines (and most with longer bodies, allowing greater rudder leverage, critical for single-engine control) – came out on the opposite end of the rankings, with one of the lowest rates of engine-failure accidents of all "light" twins examined, at only 0.4 per hundred-thousand hours.

## Variants

* Certified from 1954, the seven-seat 560 is powered by two 270–295 hp (201–220 kW) Lycoming GO-480s.
* From 1955, the 680 has Supercharged 340–380 hp (250–280 kW) Lycoming GSO-480s.
* From 1958, the lighter 500 is powered by two 250–290 hp (190–220 kW) Lycoming O-540s or Continental IO-470s.
* From 1963, the stretched 680-FL offered up to eleven seats.
* It gained two 575 hp (429 kW) AiResearch TPE-331 turboprops from the 680-T in 1965.
* From 1971, the heavier 690 has a larger wing and more powerful 717.5–748 hp (535–558 kW) TPE-331s.
* From 1979, the final 695 Jetprop 980/1000 is powered by 733–820 hp (547–611 kW) TPE-331s.
Type certificate data sheet 6A1 and 2A4 :
| model | name | approved | TC | engines | power | MTOW | ceiling | seats | fuel | built |
| L-3805 | | | | | | | | | | 1 |
| 520 | | 1952-01-31 | 6A1 | 2× GO-435-C2/C2B | 2× 260 | 5500-5700 | | 5 | 145 | 150 |
| 560 | | 1954-05-28 | 6A1 | 2× GO-480-B/B1C | 2× 270 | 6000 | | 7 | 145 | 80 |
| 520 with more power, increased weight, swept tail, plus revised wing, landing gear, fuselage, and primary control system ||||||||||
| 560A | | 1955-07-01 | 6A1 | 2× GO-480-D/C/G | 2× 275 | 6000 | | 7 | 156 | |
| 560 with longer fuselage, revised engine installation, wing, landing gear, fuel and oil systems ||||||||||
| 560E | | 1957-02-21 | 6A1 | 2× GO-480-C/G | 2× 295 | 6500 | | 7 | 223 | 93 |
| 560A with Larger wings and greater payload, revised engine installation, wing, wheel and brake installation, fuel system with outboard tanks, and landing gear location ||||||||||
| 560F | | 1961-02-08 | 2A4 | 2× IGO-540-B | 2× 350 | 7500 | | 7 | 223 | |
| 680F with normally aspirated engine and reduced gross weight ||||||||||
| 360 | | | | | 2× 180 | | | 4 | | 1 |
| Lightened 560E ||||||||||
| 500 | | 1958-07-24 | 6A1 | 2× O-540-A2B | 2× 250 | 6000 | | 7 | 156 | 101 |
| 560E with decreased gross weight, powerplants, and 560A landing gear ||||||||||
| 500A | Aero Commander | 1960-04-07 | 6A1 | 2× IO-470-M | 2× 260 | 6000 | | 7 | 156 | 99 |
| 500 with new nacelles, fuel injected Continental engines and new landing gear ||||||||||
| 500B | | 1960-07-13 | 6A1 | 2× IO-540-B/E | 2× 290 | 6750 | | 7 | 156 | 217 |
| 500A with Lycoming engines and 3-bladed props. ||||||||||
| 500U | Shrike Commander | 1964-12-11 | 6A1 | 2× IO-540-E | 2× 290 | 6750 | | 7 | 156 | 56 |
| 500B with pointed nose and squared off tail. ||||||||||
| 500S | Shrike Commander | 1968-03-15 | 6A1 | 2× IO-540-E | 2× 290 | 6750 | | 7 | 156 | 316 |
| 500U with minor changes ||||||||||
| 680 Super | L-26C → U-4B L-26C → U-9C | 1955-10-14 | 2A4 | 2× GSO-480-A1A6 | 2× 340 | 7000 | | 7 | 223 | 254 |
| supercharged 560A ||||||||||
| 680E | | 1958-06-19 | 2A4 | 2× GSO-480-B1A6 | 2× 340 | 7500 | | 7 | 223 | 100 |
| 680 with Lightened 560E/560A type undercarriage, extended wing and increased maximum weight ||||||||||
| 720 | AltiCruiser | 1958-12-05 | 2A4 | 2× GSO-480-B1A6 | 2× 340 | 7500 | | 6 | 223 | 13 |
| Pressurized 680-E, structural modifications to the fuselage, extended wing and increased maximum weight ||||||||||
| 680F | | 1960-08-23 | 2A4 | 2× IGSO-540-B | 2× 380 | 8000 | | 7 | 223 | 126 |
| 680E with fuel injection engine, new nacelles, new main gear and increased maximum weight ||||||||||
| 680FP | | | | | 2× 380 | | | | 223 | 26 |
| Pressurized 680F ||||||||||
| 680FL | Grand Commander | 1963-05-24 | 2A4 | 2× IGSO-540-B | 2× 380 | 7000-8500 | | 11 | 223 | 157 |
| 680F with larger tail, 2 built for the US Army as the RL-26D → RU-9D with SLAR, Courser Commander after 1967; stretched ||||||||||
| 680FL(P) | Grand Commander | 1964-10-08 | 2A4 | 2× IGSO-540-B1A/B1C | 2× 380 | 8500 | | 11 | 223 | 37 |
| pressurized 680FL ||||||||||
| 680T | Turbo Commander | 1965-09-15 | 2A4 | 2× TPE-331-43 | 2× 575 | 8950 | 25,000 ft | 11 | 286.5 | 56 |
| 680FL/P turboprop ||||||||||
| 680V | Turbo Commander | 1967-06-13 | 2A4 | 2× TPE-331-43 | 2× 575 | 9400 | 25,000 ft | 11 | 286.5 | 36 |
| 680T with slightly improved cargo capacity ||||||||||
| 680W | Turbo II Commander | 1968-02-05 | 2A4 | 2× TPE-331-43BL | 2× 575 | 9400 | 25,000 ft | 11 | 286.5 | 46 |
| 680V with pointed nose. squared off fin, one panoramic and two small cabin windows and weather radar ||||||||||
| 681 | Hawk Commander | 1969-03-20 | 2A4 | 2× TPE-331-43BL | 2× 575 | 9400 | 25,000 ft | 11 | 286.5 | 43 |
| 680W with improved pressurisation, air conditioning system and nose ||||||||||
| 681B | Turbo Commander | | | | | | 25,000 ft | | | 29 |
| Marketing designation for economy version of the 681 ||||||||||
| 685 | Commander | 1971-09-17 | 2A4 | 2× GTSIO-520-F/K | 2× 435 | 9000 | 25,000 ft | 9 | 256-322 | 66 |
| 690 powered by piston engines ||||||||||
| 690 | Commander 690 | 1971-07-19 | 2A4 | 2× TPE-331-5 | 2× 717.5 | 10250 | 25,000 ft | 11 | 384 | 79 |
| 681 with new wing centre section and engines moved further outboard ||||||||||
| 690A | Commander 690A | 1973-04-25 | 2A4 | 2× TPE-331-5 | 2× 717.5 | 10250 | 31,000 ft | 11 | 384 | 245 |
| 690 with changed flightdeck layout and increased pressurisation ||||||||||
| 690B | Commander 690B | 1976-10-05 | 2A4 | 2× TPE-331-5 | 2× 717.5 | 10325 | 31,000 ft | 10 | 384 | 217 |
| 690A with improved soundproofing and internal lavatory ||||||||||
| 690C | Jetprop 840 | 1979-09-07 | 2A4 | 2× TPE-331-5 | 2× 717.5 | 10325 | 31,000 ft | 11 | 384 | 136 |
| 690B with increased wingspan, wet wing fuel tanks and winglets ||||||||||
| 690D | Jetprop 900 | 1981-12-02 | 2A4 | 2× TPE 331-5 | 2× 748 | 10700 | 31,000 ft | 11 | 425-474 | 42 |
| 690C with internal rear cabin extension, improved pressurisation and five square cabin windows ||||||||||
| 695 | Jetprop 980 | 1979-11-01 | 2A4 | 2× TPE-331-10 | 2× 733 | 10325 | 31,000 ft | 11 | 425-474 | 84 |
| more powerful 690C ||||||||||
| 695A | Jetprop 1000 | 1981-04-30 | 2A4 | 2× TPE-331-10 | 2× 820 | 11200 | 35,000 ft | 11 | 474 | 101 |
| more powerful 690D with higher takeoff weight, built for the NOAA ||||||||||
| 695B | Jetprop 1000B | 1984-02-15 | 2A4 | 2× TPE-331-10 | 2× 820 | 11750 | 35,000 ft | 11 | 474 | 6 |
| 695A with minor changes ||||||||||

## Operators
### Government operators
#### United States

* Texas Highway Patrol

#### Indonesia

* Indonesian National Police

### Military operators
#### Algeria

* Algerian Air Force – 1 x 680E survey aircraft in 1986

#### Angola

* Angolan Air Force – 1 x 690A VIP aircraft in 1986

#### Argentina

* Argentine Air Force – 1 x 500B, 27 x 500U and 1 x 680
* Argentine Army Aviation – 680V, 690A

#### Bahamas

* Royal Bahamas Defence Force – 500S (no longer operated)

#### Benin

* Benin Air Force – 1 x 500B

#### Bolivia

* Bolivian Air Force – 1 x 690 in 1986

#### Burkina Faso

* Burkina Faso Air Force – 1 x 500B in 1986

#### Colombia

* Colombian Aerospace Force
* National Army of Colombia

#### Costa Rica

* Public Force of Costa Rica

#### Cuba

* Cuban Air Force – 1 × 560 acquired in late 1956.

#### Dominican Republic

* Air Force of the Dominican Republic

#### Greece

* Hellenic Army – 2 x 680FL

#### Guatemala

* Guatemalan Air Force

#### Honduras

* Honduran Air Force

#### Indonesia

* Indonesian Army Aviation Command – 2 x 680FL

#### Iran

* Islamic Republic of Iran Air Force – 3 x 681B
* Islamic Republic of Iran Army Aviation – 3 x 690, 2 x 690A
* Islamic Republic of Iran Navy Aviation – 2 x 500S, 2 x 690, 6 x 690A

#### Ivory Coast

* Ivory Coast Air Force – 1 x 500B

#### Kenya

* Kenya Air Force – 1 x 680FP (no longer operated)

#### Kingdom of Laos

* Royal Lao Air Force – 1 x 560 (no longer operated)

#### Republic of Korea

* Republic of Korea Air Force – 3 x 520, 2 x 560F

#### Mexico

* Mexican Air Force – 20 x 500S

#### Nicaragua

* Fuerza Aérea de la Guardia Nacional

#### Niger

* Niger Air Force – 1 x 500B

#### Pakistan

* Pakistan Air Force – 1 x 680E (with radar nose), 1 x 680F
* Pakistan Army Aviation – 1 x 690B

#### Panama

* Panamanian Air Force

#### Philippines

* Philippine Air Force - 2 Units for ELINT.

#### Thailand

* Royal Thai Air Force

#### United States

* United States Air Force as the L-26 and U-4
* United States Army as the L-26 and U-9

#### Venezuela

* Bolivarian Navy of Venezuela

### Civil operators
#### Samoa

* Talofa Airways

## Notable accidents

* On 19 June 1964 Senator Ted Kennedy was a passenger in an Aero Commander 680 airplane flying in bad weather from Washington, D.C., to Massachusetts. It crashed into an apple orchard in the western Massachusetts town of Southampton on the final approach to the Barnes Municipal Airport near Westfield. The pilot and Edward Moss, one of Kennedy's aides, were killed. Kennedy suffered a severe back injury, a punctured lung, broken ribs and internal bleeding.
* World War II hero and actor Audie Murphy died in an Aero Commander 680 crash while flying as a passenger on 28 May 1971. The aircraft was flying in bad weather at night and was on approach to Roanoke, Virginia when it flew into the side of Brush Mountain outside Blacksburg, Virginia, West of Roanoke. Four others and the pilot were also killed.
* On 11 August 2002 photographer Galen Rowell, his wife Barbara Cushman Rowell, pilot Tom Reid and Reid's friend Carol McAffee were killed in an Aero Commander 690 crash near Eastern Sierra Regional Airport in Bishop, California.
* On Sunday 2 October 1994, an Aero Commander 690 operated by Seaview Air as flight CD111 departed for from Williamtown, NSW, on a flight to Lord Howe Island. Eight passengers, including honeymooners and a family with two children, boarded the single-pilot aircraft. 30 minutes after departure a distress call was made by the pilot with no future communications made. Only some minor wreckage was ever recovered. During the investigation a number of safety breaches by the operator were discovered including regular operations with overweight aircraft, inaccessible safety equipment & illegal regular public transport operations when the operator was only approved to operate charter flights. The incident was a significant one to occur in Australia & lead to a $20 million royal commission which resulted into fundamental changes to the governing aviation body in Australia.

## Specifications (Rockwell Aero Commander 500S)

Data from Jane's all the world's aircraft 1976–77.
General characteristics
* Crew: Two
* Capacity: four passengers
* Length: 36 ft 9.75 in (11.22 m)
* Wingspan: 49 ft 0.5 in (14.95 m)
* Height: 14 ft 6 in (4.42 m)
* Wing area: 255 sq ft (23.69 m$^2$)
* Aspect ratio: 9.45:1
* Airfoil: NACA 23012 modified
* Empty weight: 4,635 lb (2,102 kg)
* Max takeoff weight: 6,750 lb (3,062 kg)
* Powerplant: 2 × Lycoming IO-540-E1B5 air-cooled flat-six piston engines, 290 hp (216 kW) each
Performance
* Maximum speed: 215 mph (346 km/h, 187 kn) at sea level (TAS)
* Cruise speed: 203 mph (326 km/h, 176 kn) at 9,000 ft (2,750 m), 75% power, TAS
* Stall speed: 68 mph (109 km/h, 59 kn) flaps and landing gear down, CAS
* Minimum control speed: 75 mph (121 km/h, 65 kn)
* Range: 1,078 mi (1,735 km, 936 nmi)
* Service ceiling: 19,400 ft (5,913 m)
* Rate of climb: 1,340 ft/min (6.8 m/s)